U.S. patent application number 13/581001 was filed with the patent office on 2012-12-13 for uv coating composition for led color conversion.
Invention is credited to Hyun-Seop Shim.
Application Number | 20120313045 13/581001 |
Document ID | / |
Family ID | 44507050 |
Filed Date | 2012-12-13 |
United States Patent
Application |
20120313045 |
Kind Code |
A1 |
Shim; Hyun-Seop |
December 13, 2012 |
UV COATING COMPOSITION FOR LED COLOR CONVERSION
Abstract
A UV coating composition for LED color conversion including: 25
wt % to 97 wt % of a UV curable resin; and 3 wt % to 75 wt % of a
phosphor. The composition enables emission of white light using
only a white LED lens or a light guide plate without affecting a
blue, violet or UV LED, thereby eliminating a need for a white LED.
Further, users of a LED including the composition can perform
direct and easy adjustment of the intensity of white light to
obtain a desired intensity by replacing a conventional LED lens.
The LED lens provides soft and comfortable lighting which
effectively reduces glare caused by high brightness white LED
lighting. Moreover, the composition slows deterioration of a
lighting device and makes possible a light guide plate having a
simple and thin structure.
Inventors: |
Shim; Hyun-Seop; (Seoul,
KR) |
Family ID: |
44507050 |
Appl. No.: |
13/581001 |
Filed: |
August 12, 2010 |
PCT Filed: |
August 12, 2010 |
PCT NO: |
PCT/KR10/05285 |
371 Date: |
August 24, 2012 |
Current U.S.
Class: |
252/301.36 |
Current CPC
Class: |
C09D 133/04 20130101;
C09K 11/613 20130101; G02B 6/0016 20130101; G02B 6/0038 20130101;
C09K 11/641 20130101; C09K 11/7784 20130101; H01L 33/502 20130101;
C09K 11/642 20130101; C08K 3/10 20130101; C09D 7/69 20180101; C09K
11/7701 20130101; G02B 6/0068 20130101; G02B 6/0046 20130101; C09K
11/7706 20130101; C08L 33/12 20130101; C09K 11/7734 20130101; H01L
33/501 20130101; C09K 11/7407 20130101; Y02B 20/00 20130101; Y02B
20/181 20130101; C09D 7/68 20180101; C09K 11/7731 20130101; G02B
6/0073 20130101; G02B 6/0023 20130101; C09K 11/7774 20130101; C08F
222/1065 20200201; C08F 222/1067 20200201 |
Class at
Publication: |
252/301.36 |
International
Class: |
C09K 11/78 20060101
C09K011/78; C09K 11/84 20060101 C09K011/84; C09K 11/80 20060101
C09K011/80; C09K 11/64 20060101 C09K011/64; C09K 11/81 20060101
C09K011/81; C09K 11/66 20060101 C09K011/66; C09K 11/79 20060101
C09K011/79; C09K 11/77 20060101 C09K011/77; C09K 11/67 20060101
C09K011/67; C09K 11/08 20060101 C09K011/08; C09K 11/74 20060101
C09K011/74 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 24, 2010 |
KR |
10-2010-0016560 |
Mar 24, 2010 |
KR |
10-2010-0026164 |
Claims
1. A UV coating composition for LED color conversion comprising:
25.about.97 wt % of a UV-curable resin; and 3.about.75 wt % of a
phosphor for color conversion.
2. A UV coating composition for LED color conversion comprising:
25.about.96.99 wt % of a UV-curable resin; 3.about.65 wt % of a
phosphor for color conversion; and 0.01.about.10.0 wt % of light
diffusing beads having an average particle diameter of 0.2.about.30
.mu.m.
3. The UV coating composition according to claim 1, wherein the
UV-curable resin is at least one selected from the group consisting
of urethane acrylate, epoxy acrylate, polyester acrylate, and acryl
acrylate resins.
4. The UV coating composition according to claim 1, wherein the
phosphor for color conversion comprises a yellow phosphor selected
from YAG-based (YGd).sub.3Al.sub.5O.sub.12:Ce and
Sr.sub.2Ga.sub.2S.sub.5:Eu.sup.2+ to convert blue light emitted
from a blue LED into white light.
5. The UV coating composition according to claim 1, wherein the
phosphor for color conversion comprises a red phosphor and a green
phosphor to convert blue light emitted from a blue LED into white
light, the red phosphor being selected from Y.sub.2O.sub.2S:Eu,Gd,
Li.sub.2TiO.sub.3:Mn, LiAlO.sub.2:Mn,
6MgO.As.sub.2O.sub.5:Mn.sup.4+ and
3.5MgO.0.5MgF.sub.2.GeO.sub.2:Mn.sup.4+, the green phosphor being
selected from ZnS:Cu,Al, Ca.sub.2MgSi.sub.2O.sub.7:Cl,
Y.sub.3(Ga.sub.xAl.sub.1-x).sub.5O.sub.12:Ce (0<x<1),
La.sub.2O.sub.3.11Al.sub.2O.sub.3:Mn and
Ca.sub.8Mg(SiO.sub.4).sub.4C.sub.12:Eu,Mn.
6. The UV coating composition according to claim 5, wherein the red
phosphor and the green phosphor are mixed in a weight ratio of
1:0.2.about.1.2.
7. The UV coating composition according to claim 1, wherein the
phosphor for color conversion comprises a red phosphor, a green
phosphor and a blue phosphor to convert light emitted from a violet
LED or a UV LED into white light, the red phosphor being selected
from Y.sub.2O.sub.2S:Eu,Gd, Li.sub.2TiO.sub.3:Mn, LiAlO.sub.2:Mn,
6MgO.As.sub.2O.sub.5:Mn.sup.4+ and
3.5MgO.0.5MgF.sub.2.GeO.sub.2:Mn.sup.4+, the green phosphor being
selected from ZnS:Cu,Al, Ca.sub.2MgSi.sub.2O.sub.7:Cl,
Y.sub.3(Ga.sub.xAl.sub.1-x).sub.5O.sub.5O.sub.12:Ce (0<x<1),
La.sub.2O.sub.3.11Al.sub.2O.sub.3:Mn and
Ca.sub.8Mg(SiO.sub.4).sub.4C.sub.12:Eu,Mn, the blue phosphor being
selected from BaMgAl.sub.10O.sub.17 and
(Sr,Ca,BaMg).sub.10(PO.sub.4).sub.6Cl.sub.2:Eu.
8. The UV coating composition according to claim 7, wherein the red
phosphor, the blue phosphor, and the green phosphor are mixed in a
weight ratio of 1:0.2.about.1.2:0.2.about.1.2.
10. The UV coating composition according to claim 1, further
comprising: 0.1.about.3.0 wt % of a pigment.
11. The UV coating composition according to claim 2, wherein the
light diffusing beads comprise a mixture of light diffusing beads
having average particle diameters of 1.about.4 .mu.m, 5.about.10
.mu.m and 11.about.30 .mu.m and mixed in a weight ratio of
1:0.4.about.0.8:0.1.about.0.3.
12. The UV coating composition according to claim 2, wherein the
UV-curable resin is at least one selected from the group consisting
of urethane acrylate, epoxy acrylate, polyester acrylate, and acryl
acrylate resins.
13. The UV coating composition according to claim 2, wherein the
phosphor for color conversion comprises a yellow phosphor selected
from YAG-based (YGd).sub.3Al.sub.5O.sub.12:Ce and
Sr.sub.2Ga.sub.2S.sub.5:Eu.sup.2+ to convert blue light emitted
from a blue LED into white light.
14. The UV coating composition according to claim 2, wherein the
phosphor for color conversion comprises a red phosphor and a green
phosphor to convert blue light emitted from a blue LED into white
light, the red phosphor being selected from Y.sub.2O.sub.2S:Eu,Gd,
Li.sub.2TiO.sub.3:Mn, LiAlO.sub.2:Mn,
6MgO.As.sub.2O.sub.5:Mn.sup.4+ and
3.5MgO.0.5MgF.sub.2.GeO.sub.2:Mn.sup.4+, the green phosphor being
selected from ZnS:Cu,Al, Ca.sub.2MgSi.sub.2O.sub.7:Cl,
Y.sub.3(Ga.sub.xAl.sub.1-x).sub.5O.sub.12:Ce (0<x<1),
La.sub.2O.sub.3.11Al.sub.2O.sub.3:Mn and
Ca.sub.8Mg(SiO.sub.4).sub.4C.sub.12:Eu,Mn.
15. The UV coating composition according to claim 14, wherein the
red phosphor and the green phosphor are mixed in a weight ratio of
1:0.2.about.1.2.
16. The UV coating composition according to claim 2, wherein the
phosphor for color conversion comprises a red phosphor, a green
phosphor and a blue phosphor to convert light emitted from a violet
LED or a UV LED into white light, the red phosphor being selected
from Y.sub.2O.sub.2S:Eu,Gd, Li.sub.2TiO.sub.3:Mn, LiAlO.sub.2:Mn,
6MgO.As.sub.2O.sub.5:Mn.sup.4+ and
3.5MgO.0.5MgF.sub.2.GeO.sub.2:Mn.sup.4+, the green phosphor being
selected from ZnS:Cu,Al, Ca.sub.2MgSi.sub.2O.sub.7:Cl,
Y.sub.3(Ga.sub.xAl.sub.1-x).sub.5O.sub.12:Ce (0<x<1),
La.sub.2O.sub.3.11Al.sub.2O.sub.3:Mn and
Ca.sub.8Mg(SiO.sub.4).sub.4C.sub.12:Eu,Mn, the blue phosphor being
selected from BaMgAl.sub.10O.sub.17 and
(Sr,Ca,BaMg).sub.10(PO.sub.4).sub.6Cl.sub.2:Eu.
17. The UV coating composition according to claim 16, wherein the
red phosphor, the blue phosphor, and the green phosphor are mixed
in a weight ratio of 1:0.2.about.1.2:0.2.about.1.2.
18. The UV coating composition according to claim 2, further
comprising: 0.1.about.3.0 wt % of a pigment.
Description
TECHNICAL FIELD
[0001] The present invention relates to a UV coating composition
for LED (light emitting diode) color conversion. More particularly,
the present invention relates to a UV coating composition for LED
color conversion, which includes a phosphor for color conversion
and, optionally, a light diffusing bead and/or a pigment, in a
heat-resistant transparent UV-curable matrix resin to allow white
light for lighting or a display device to be obtained through a
simple and inexpensive structure from a high brightness blue LED,
violet LED or UV LED having a long lifespan without using an
expensive white LED having a relatively short lifespan and high
brightness, which has a flat coating surface such that the phosphor
for color conversion can be uniformly distributed and coated
thereon, which can provide smoother and more comfortable
illumination by effectively relieving glare due to high brightness
of the LED when applied to lighting, and which permits compactness
and structural simplification when applied to a display device.
BACKGROUND ART
[0002] An LED is a semiconductor device which converts electrical
energy into light using characteristics of a semiconductor
including specific compounds. The LED has various advantages, such
as very small power consumption is due to high light conversion
efficiency, appropriateness for miniaturization, slimming and
weight reduction and unlimited applicability due to its small light
source, semi-permanent and long lifespan (a blue, violet, or UV LED
has a lifespan of about 100,000 hours, and a white LED has a
lifespan of about 30,000 hours), very high response speed due to no
need for pre-heating by elimination of the use of
thermoluminescence or electroluminescence, a very simple lighting
circuit, high impact resistance, safety and few environmental
pollution factors due to no use of discharge gas and no filament,
pulse operation at high repetition rate, reduction in visual
fatigue, and realization of full color. Accordingly, the LED is
widely used for light sources for liquid crystal display (LCD)
backlights of mobile phones, camcorders, digital cameras, personal
digital assistants (PDAs), etc., traffic lamps, electronic display
boards, car headlights/taillights, display lamps of various kinds
of electronic devices, office machines, facsimiles, etc., night
lighting of remote controllers or surveillance cameras, infrared
communication devices, information displays of outdoor advertising
boards using various combinations of RGB pixels, ultra-precision
displays of electronic display boards, and high-efficiency
indoor/outdoor lighting. Particularly, as a high-brightness LED
solving general problems of a conventional LED such as low
brightness is commercially available, the use and application of
the high-brightness LED have been rapidly expanded.
[0003] Particularly, since a white LED is very useful as a light
source for an LCD backlight and indoor/outdoor lighting, usage has
thereof rapidly increased. Also, just as fluorescent lamps drove
incandescent lamps out of the market, it is expected that LED lamps
will drive fluorescent lamps from the market.
[0004] A method for obtaining white light by an LED will be
described hereinafter.
[0005] First, in a classical method for obtaining white light,
three types of LEDs, that is, a red LED, a green LED, and a blue
LED, are combined to obtain white light. However, this method has
problems in that it requires a relatively high manufacturing cost,
increases product size due to a complicated operating circuitry,
and provides low optical characteristics and reliability of the
product due to difference in temperature characteristics of the
three LEDs, and thus is not substantially used at present.
[0006] Recently, in another method for obtaining white light, a
white LED is selected as a single LED for generating white light.
In this method, the surface of the white LED is coated with a
phosphor, or the periphery of the LED or a lens is molded together
with the phosphor such that the phosphor can be excited by light
emitted from the LED and having a specific wavelength to generate
light having a different wavelength. Then, the generated light is
mixed with the light emitted from the single LED chip to generate
white light.
[0007] However, in such a conventional method, the surface of a
blue, violet or UV LED is directly coated with a phosphor, or the
periphery of the LED or the lens is molded together with the
phosphor. Thus, this method has a problem in that the lifespan of
the LED is significantly reduced to one third or less due to LED
degradation resulting from deterioration in heat dissipation.
Particularly, when the phosphor is not evenly coated or dispersed,
luminescent colors becomes non-uniform. However, it is very
difficult to achieve uniform coating or dispersion/distribution of
the phosphor.
[0008] As one of the most widely used white LEDs, U.S. Pat. No.
5,998,925 (Nichia Corp.) discloses a white LED, in which an
InGaN-based blue LED emitting blue light having a wavelength of 450
nm is coated or molded with a yellow phosphor (generally,
yttrium-aluminum-garnet:Y3Al5O12:Ce, YAG-based compound) such that
blue light emitted from the blue LED excites the YAG yellow
phosphor to emit yellow light in a wide peak, thereby allowing
light components in two different wavelength bands, that is, the
narrow-peak blue light of the blue LED and the wide-peak yellow
light of the YAG-based yellow phosphor, to be recognized as white
light by human's eyes a viewer through complementary
interference.
[0009] However, the white light results from a mixture of the light
components, which have different wavelengths and are not in a
complete completely complementary relationship, and thus has only
part of a visible range spectrum. For this reason, the white light
has a color rendering index (CRI) of about 60.about.75, and is
generally not accepted as near-natural white light. Thus, it does
not satisfy requirements for general indoor lighting. Also, the
white LED has a problem of low brightness, because the blue LED
shows the highest efficiency by excitation light at a wavelength of
about 405 nm whereas the YAG-based phosphor is excited by blue
light in a wavelength band of 450.about.460 nm. Particularly, in
coating or molding of the YAG-based phosphor, it is difficult to
guarantee homogeneous and uniform dispersibility, thereby
deteriorating uniformity and reproducibility of products in terms
of brightness and spectral distribution of white light, and
significantly reducing the lifespan of the LED.
[0010] In order to overcome the problems of the white LED including
the blue LED and the YAG-based phosphor, U.S. Pat. No. 5,952,681
(Solidlite Corp.) discloses a technology for obtaining
three-wavelength, high-CRI and near-natural white light by
combining red, green and blue phosphors, and using a high
brightness UV LED, which emits light in a wavelength band of 250 nm
to 390 nm as an excitation light source. However, the use of the
white LED has a problem in that the blue and green phosphors have
satisfactory light emission efficiency while the red phosphor has
low light emission efficiency. Particularly, the UV LED tends to
deteriorate an organic resin by UV having a strong energy, thereby
significantly reducing the lifespan of the LED.
[0011] In another type of white LED (Solidlite Corp.), a violet LED
emitting light in a wavelength band of 390 nm to 410 nm is used and
white light is obtained by combining red, blue, and green
phosphors. The high brightness violet LED is commercially available
from Cree Corporation (U.S.), and is known to emit a relatively
natural three-wavelength band white light through uniform light
emission from red, blue, and green phosphors excited by violet
light in a wavelength band of 390 nm to 410 nm.
[0012] Factors affecting the characteristics of white light emitted
from a white LED may include the intensity of the light,
combination applicability of the light emitted from the LED and
light converted by a phosphor, and the components, content and
dispersed state of the phosphor. These factors have a significant
influence on the emitted light. Particularly, white light emitted
by combination of the blue LED and the YAG-based phosphor may have
a problem in that the emitted color is generally biased to blue or
yellow color due to difficulty in adjustment of the amount of a
yellow phosphor and uniform dispersion thereof.
[0013] In order to obtain a white LED having excellent luminescent
characteristics, it is necessary for a phosphor to be evenly
dispersed in a light-transmitting matrix resin. However, in a
fabrication process, before the matrix resin is completely
hardened, a phosphor having a much higher specific gravity (the
phosphor has a specific gravity of about 3.8.about.6.0, although it
depends on the kind of the phosphor) than the matrix resin is
precipitated in a lower region of the light-transmitting matrix
resin having a low specific gravity (for example, an epoxy resin
has a specific gravity of about 1.1.about.1.5), thereby making it
difficult to obtain white light having excellent luminescent
characteristics. Furthermore, it is not easy to precisely control
the degree of dispersion of the phosphor. Accordingly, it is not
easy to fabricate a high-quality white LED device and fabrication
reproducibility is not good.
[0014] Meanwhile, an LED lighting device includes an LED lens,
which allows light components diffused and emitted from an LED upon
application of voltage to be directed as parallel light beams and
can increase the intensity of radiation through a viewing angle. In
addition, the viewing angle is adjusted by controlling curvatures
of a light-incident lower surface and a light-emitting upper
surface of the lens, and the lens can be suitably selected and used
according to various shapes and sizes of lenses based on various
parameters, such as the kind and power of a used LED, use purpose,
an end user preference, desired intensity of lighting, and the
like.
[0015] FIG. 1 is a sectional view of a conventional LED lens. The
conventional LED lens generally has a hemispherical shape with a
wide upper section and a narrow lower section, without being
limited thereto. The LED lens includes an upper surface 7a having
an annular lateral portion 7 and a flange 8, and is formed on a
lower surface thereof with a cylindrical LED mounting portion 9.
The LED mounting portion 9 may have a flat shape, but is generally
formed with an internally convex portion 12 for collection of
light.
[0016] The upper surface 7a of the LED lens may have a pectination
shape, a plurality of dots, or a smooth planar shape in order to
provide soft illumination. Also, the upper surface of the LED lens
may have an opening at the center thereof. The lateral portion 7
may have various angle-gradients and lengths for adjustment of an
irradiation angle. Further, the upper surface 7a may be formed into
a forwardly projecting convex shape, a flat shape, a concave shape,
or other specific shapes.
[0017] Reference numeral 5 denotes a substrate and reference
numeral 6 denotes a light diffusing lens for LED molding.
[0018] FIG. 2 is an exploded perspective view of a conventional
edge-type backlight unit. The conventional backlight unit 100'
generally includes a light source 15a, a light guide plate 10'
having one end facing the light source 15a, a reflective sheet 20
disposed below the light guide plate 10', a prism sheet 30 disposed
above the light guide plate 10', a light diffusing sheet 40
disposed above the prism sheet 30, and a protective sheet 50
disposed above the light diffusing sheet 40.
[0019] More specifically, a light source 15 includes a linear light
source 15a or a white LED (not shown) and a reflective plate 15b,
and is located adjacent to a thick side surface of the light guide
plate 10' that generally has a tapered shape. The reflective sheet
20 is located below the light guide plate 10', and the prism sheet
30, the light diffusing sheet 40 and the protective sheet 50 are
sequentially stacked on an upper surface of the light guide plate
10'. The prism sheet 13 has a pattern of plural prisms (not shown)
parallel to each other.
[0020] The light guide plate 10' is formed with a light exiting
surface 11 on an upper surface thereof and has a lower surface 13
adjoining the reflective sheet 20. A flat light entering surface 12
is formed on one side surface of the light guide plate adjacent to
the light source 15, and the lower surface 13 of the light guide
plate 10' is formed with a pattern of plural prisms 14 each having
prism slopes 14a, 14b and parallel to each other in a direction
orthogonal to a traveling direction of light emitted from the light
source 15.
[0021] Here, light emitted from the light source 15 is received by
the flat light entering surface 12 and is scattered by the prism
slopes 14a, 14b of the prisms 14 under the light guide plate 10'.
Then, the light is emitted toward the prism sheet 30 through the
light exiting surface 11 of the light guide plate 10' and is
scattered again by the prism sheet 30 having the pattern of plural
prisms (not shown) orthogonal to the pattern of prisms 14, which is
formed on the lower surface 13 of the light guide plate 10'. Then,
the light is converted into uniform light and output through the
light diffusing sheet 40.
[0022] Since the light diffusing sheet 40 serves to convert
incident light into uniform light over the entire area of a display
panel through diffusion and scattering, stacking the light
diffusing sheet 40 on the prism sheet 30 makes it difficult to
reduce the thickness of the backlight unit and increases the number
of processes and components, causing deterioration in economic
feasibility and process efficiency.
DISCLOSURE
Technical Problem
[0023] Therefore, it is an object of the present invention to
achieve significant increase in lifespan of an LED lighting device
for emission of white light, in which a high brightness LED having
a long lifespan (lifespan of about 100,000 hours), such as a blue
LED, a violet LED, and optionally a UV LED, is used to provide
while light for lighting or for a display device through a hard
thin film for surface protection, instead of a conventional high
brightness white LED having a relatively short lifespan (lifespan
of about 30,000 hours).
[0024] It is another object of the present invention to allow a
user or an operator, instead of a manufacturer, to perform direct
and easy adjustment of the intensity of white light to a desired
intensity at low cost, or to obtain soft white light through a
relatively inexpensive LED, such as a blue LED, a violet LED or a
UV LED, instead of a conventional expensive high brightness white
LED.
[0025] It is a further object of the present invention to achieve
effective and easy removal of a possibility of non-uniformity in
emitted colors resulting from non-uniform distribution or coating
of a phosphor for light conversion.
[0026] It is yet another object of the present invention to obtain
soft and comfortable lighting by effectively reducing glare caused
by high brightness white LED lighting.
[0027] It is yet another object of the present invention to reduce
a possibility of deterioration of a lighting device by ensuring
high heat resistance.
[0028] It is yet another object of the present invention to provide
a backlight unit having a thin and simple structure and high
durability using a light guide plate for color conversion.
Technical Solution
[0029] The above and other objects of the present invention can be
achieved by the provision of a UV coating composition for LED color
conversion, which include 25.about.97 percent by weight (wt %) of a
UV-curable resin, preferably 40.about.95 wt % of the UV curable
resin, and 3.about.75 wt % of a phosphor for color conversion,
preferably 5.about.60 wt % of the phosphor for color
conversion.
[0030] In addition, the above and other objects of the present
invention can be achieved by the provision of a UV coating
composition for LED color conversion, which include: 25.about.96.99
wt % of a UV-curable resin, preferably 45.about.94.99 wt % of the
UV-curable resin; 3.about.65 wt % of a phosphor for color
conversion, preferably 5.about.50 wt % of the phosphor for color
conversion; and 0.01.about.10.0 wt % of light diffusing beads
having an average particle diameter of 0.2.about.30 .mu.m,
preferably an average particle diameter of 0.5.about.5 .mu.m,
specifically an average particle diameter of 1.0.about.3.5 .mu.m,
preferably 0.01.about.5.0 wt % of the light diffusing beads.
[0031] The UV coating composition for LED color conversion may
further include 0.1.about.3.0 wt % of a pigment, preferably
0.1.about.1.0 wt % of the pigment.
[0032] The UV-curable resin may include at least one selected from
the group consisting of urethane acrylate, epoxy acrylate,
polyester acrylate, and acryl acrylate resins.
Advantageous Effects
[0033] With the UV coating composition for LED color conversion
according to the present invention, a lighting device can emit
white light, as in a conventional white light LED, independently
using only a white LED lens or a light guide plate without
affecting a blue, violet or UV LED, thereby eliminating a need for
a white LED which is relatively expensive and has a short lifespan
of about 1/3 that of other kinds of LEDs. Further, when the
lighting device employs a conventional blue, violet, or UV LED
having a long lifespan, the UV coating composition of the present
invention allows the lighting device to obtain white light by
simply and easily replacing a lens. Thus, an LED lens comprising
the UV coating composition of the present invention allows a user
or an operator, instead of a manufacturer, to perform direct and
easy adjustment of the intensity of white light to a desired
intensity by replacing a conventional LED lens, and makes it
possible to provide soft and comfortable lighting by effectively
reducing glare caused by high brightness white LED lighting.
Furthermore, the UV coating composition of the present invention
may provide a backlight unit having a simple and thin structure for
a display device and may reduce a possibility of deterioration of a
lighting device or a display device by ensuring high heat
resistance, thereby providing high efficiency and economic
feasibility.
BRIEF DESCRIPTION OF DRAWINGS
[0034] FIG. 1 is a sectional view of a conventional LED lens
[0035] FIG. 2 is an exploded perspective view of a conventional
edge-type backlight unit.
[0036] FIG. 3 is a cross-sectional view of an LED lens including a
UV coating composition for LED color conversion according to the
present invention applied to an upper surface thereof.
[0037] FIG. 4 is a view of a coating layer of the UV coating
composition for LED color conversion according to the present
invention.
[0038] FIG. 5 to FIG. 7 are perspective views of embodiments of a
backlight unit including a light guide plate having a UV coating
layer of the UV coating composition for LED color conversion
according to the present invention on a light entering or exiting
surface of the light guide plate.
BEST MODE
[0039] Embodiments of the present invention will now be described
in more detail.
[0040] First, a coating layer 1 comprised of a UV coating
composition for LED color conversion according to the present
invention will be described with reference to referring to FIG. 4.
Herein, the UV coating composition for LED color conversion
according to the present invention may often refer to the UV
coating layer 1 for LED color conversion.
[0041] As for a UV-curable matrix resin 2, any UV-curable resin
having good transparency and heat-resistance may be advantageously
used without limitation. Examples of the heat-resistant,
transparent UV-curable matrix resin 2 may include urethane
acrylate, epoxy acrylate, polyester acrylate, acryl acrylate, and
mixtures thereof. The heat-resistant, transparent matrix resin may
be present in an amount of 25.about.97 wt %, preferably 40.about.95
wt %, based on the total amount of the UV coating composition.
[0042] If the amount of the heat-resistant, transparent UV-curable
matrix resin 2 is less than 25 wt % based on the total amount of
the UV-curable composition, the composition can be deteriorated in
transparency and significantly reduce brightness due to a
backlighting effect caused by scattering. On the other hand, if the
amount of the heat-resistant, transparent matrix resin exceeds 97
wt %, the effect of emitting white light through color conversion
can become insufficient, thereby deteriorating color quality of the
lighting or display device.
[0043] All of the examples of the UV-curable matrix resin 2
described above are typical heat-resistant, transparent resins
which allow polymerization upon UV irradiation, and elaboration
thereof will be omitted herein.
[0044] Meanwhile, in the present invention, when a blue LED is
used, only YAG-based yellow phosphors known in the art may be used
as phosphors 3c, 4c for converting a lighting color into a white
color. In this case, a green phosphor and a red phosphor are
preferably used since the green and red phosphors can provide a
three-wavelength band natural white light. Also, when a violet LED
or a UV LED is used, a green phosphor, a red phosphor, and a blue
phosphor are preferably used for the same reason.
[0045] For a white LED using a blue LED and a YAG yellow phosphor,
typical examples of the YAG yellow phosphor include
(YGd).sub.3Al.sub.5O.sub.12:Ce or Sr.sub.2Ga.sub.2S.sub.5:Eu.sup.2+
developed by Nichia Corp. The YAG yellow phosphor is generally
excited by light at a wavelength of 550.about.560 nm.
[0046] Meanwhile, when a blue LED (emitting light in a wavelength
band from 425 nm to 475 nm), a green phosphor, a red phosphor, and
a blue phosphor are used, examples of the red phosphor capable of
being excited by light in a wavelength band from 430 nm to 480 nm
may include Y.sub.2O.sub.2S:Eu,Gd, Li.sub.2TiO.sub.3:Mn,
LiAlO.sub.2:Mn, 6MgO.As.sub.2O.sub.5:Mn.sup.4+, and
3.5MgO.0.5MgF.sub.2.GeO.sub.2:Mn.sup.4+, and examples of the green
phosphor capable of being excited by light in a wavelength band
from 515 nm to 520 nm may include ZnS:Cu,Al,
Ca.sub.2MgSi.sub.2O.sub.7:Cl,
Y.sub.3(Ga.sub.xAl.sub.1-x).sub.5O.sub.12:Ce (0<x<1),
La.sub.2O.sub.3.11Al.sub.2O.sub.3:Mn,
Ca.sub.8Mg(SiO.sub.4).sub.4C.sub.12:Eu, Mn, without being limited
thereto.
[0047] A three-wavelength band white LED employing a blue LED, and
red and green phosphors emits three-wavelength band white light by
generating red light and green light through excitation of a
mixture of the red and green phosphors such that the red light and
the green light are mixed with blue light from the blue LED.
[0048] In addition, the red and green phosphors capable of being
excited by the blue LED are oxides and have high stability and long
lifespan.
[0049] In the present invention, it should be noted that the
three-wavelength band white light is obtained by forming the UV
coating layer 1 for LED color conversion on a flat upper surface 7a
of an LED lens or on a flat light entering surface 12 and/or a
light exiting surface 11 of a light guide plate 10, 10a or 10b of a
display device irrespective of the LED, instead of directly or
indirectly coating a suitable mixture of the green phosphor and the
red phosphor on the blue LED.
[0050] When the UV coating layer 1 for LED color conversion is
applied to the light guide plate 10, 10a or 10b, particularly, to
the light entering surface of the light guide plate, there are
various advantages such as economic feasibility due to reduction in
amounts of phosphors, environmental friendliness due to generation
of substantially no volatile organic compounds, higher productivity
than thermosetting type resins, high scratch resistance of the
coating layer, and easy provision of anti-electrostatic or
anti-fouling properties through addition of an anti-static agent or
anti-fouling agent known in the art, as needed.
[0051] The red phosphor may be Li.sub.2TiO.sub.3:Mn at a
luminescent peak wavelength of about 659 nm, LiAlO.sub.2:Mn at a
luminescent peak wavelength of about 670 nm,
6MgO.As.sub.2O.sub.5:Mn.sup.4+ at a luminescent peak wavelength of
about 650 nm, and 3.5MgO.0.5MgF.sub.2.GeO.sub.2:Mn.sup.4+ at a
luminescent peak wavelength of about 650 nm.
[0052] The green phosphor may be
La.sub.2O.sub.3.11Al.sub.2O.sub.3:Mn at a luminescent peak
wavelength of about 520 nm, Y.sub.3(GaAl.sub.1-x).sub.5O.sub.12:Ce
(0<x<1) at a luminescent peak wavelength of about 516 nm, and
Ca.sub.8Mg(SiO.sub.4).sub.4Cl.sub.2:Eu, Mn at a luminescent peak
wavelength of about 515 nm.
[0053] The red and green phosphors may be mixed in various ratios,
and may form a neutral color LED, such as a pink or blue/white LED.
Meanwhile, the blue LED may be an InGaN, SiC, or ZnSe-based
LED.
[0054] Meanwhile, the violet LED or the UV LED may employ
BaMgAl.sub.10O.sub.17 or
(Sr,Ca,BaMg).sub.10(PO.sub.4).sub.6Cl.sub.2:Eu as a blue phosphor
as well as the green and red phosphors as described above.
[0055] Through a suitable combination of the red, blue, and green
phosphors, it is possible to obtain white light or various colors,
or obtain various colors having different color temperatures.
[0056] Of course, the obtained white light may be suitably adjusted
within a range of 3200.about.7500K through a suitable combination
of the red, blue, and green phosphors according to characteristics
of the lighting device or the display device.
[0057] The red phosphor, the blue phosphor, the green phosphor, or
a mixture 3c, 4c thereof is present in an amount of 3.about.75 wt
%, preferably 5.about.60 wt %, based on the total weight of the
composition. The blue LED may employ the red phosphor and the green
phosphor in a weight ratio of 1:0.2.about.1.2, and preferably in a
weight ratio of 1:0.3.about.0.8. The violet LED or the UV LED may
employ the red phosphor, the blue phosphor, and the green phosphor
in a weight ratio of 1:0.2.about.1.2:0.2.about.1.2, and preferably
in a weight ratio of 1:0.3.about.0.8:0.3.about.0.8.
[0058] If the phosphor 3c, 4c is included in an amount of less than
3.0 wt % based on the total weight of the composition, satisfactory
white light may not be obtained. On the other hand, if the amount
of the phosphor exceeds 60 wt %, it is disadvantageous in terms of
economic feasibility and brightness can be significantly
reduced.
[0059] Optionally, the composition according to the present
invention may further include light diffusing beads 3b, 4b.
Examples of the light diffusing beads may include: organic light
diffusing beads, such as a homopolymer or a copolymer of monomers,
selected from the group consisting of a silicon resin (index of
refraction: 1.43), polyacrylate (index of refraction: 1.49),
polyurethane (index of refraction: 1.51), polyethylene (index of
refraction: 1.54), polypropylene (index of refraction: 1.46), Nylon
(index of refraction: 1.54), polystyrene (index of refraction:
1.59), polymethylmethacrylate (index of refraction: 1.49), and
polycarbonate (1.59); inorganic light diffusing beads, such as
silica (index of refraction: 1.47), alumina (index of refraction:
1.50.about.1.56), glass (index of refraction: 1.51), CaCO.sub.3
(index of refraction: 1.51), talc (index of refraction: 1.56), mica
(index of refraction: 1.56), BaSO.sub.4 (index of refraction:
1.63), ZnO (index of refraction: 2.03), CeO.sub.2 (index of
refraction: 2.15), TiO.sub.2 (index of refraction:
2.50.about.2.71), iron oxide (index of refraction: 2.90); and
mixtures thereof.
[0060] The light diffusing beads 3b and 4b may have an average
particle diameter of 0.2.about.30 .mu.m, preferably 0.5.about.5
.mu.m, specifically 1.0.about.3.5 .mu.m, and may be present in an
amount of 0.01.about.10.0 wt %, preferably 0.01.about.5.0 wt %,
more preferably 0.01.about.2.0 wt %, based on the total weight of
the composition.
[0061] If the average particle diameter of the light diffusing
beads 3b, 4b is less than 0.2 .mu.m, the composition can be reduced
in transparency or light transmittance. On the contrary, if the
average particle diameter of the light diffusing beads exceeds 30
.mu.m, excitation of the phosphor can become insufficient or
non-uniform.
[0062] If the light diffusing beads 3b, 4b are present in an amount
of less than 0.01 wt % based on the total weight of the
composition, excitation of the phosphor can become insufficient or
non-uniform. On the contrary, if the light diffusing beads are
present in an amount of greater than 10.0 wt %, the composition can
be reduced in transparency or light transmittance.
[0063] When the light diffusing beads having an average particle
diameter of 0.2.about.30 .mu.m, preferably 0.5.about.5 .mu.m,
specifically 1.0.about.3.5 .mu.m, is present in an amount of
0.01.about.10.0 wt %, preferably 0.01.about.5.0 wt %, the amount of
the UV-curable matrix resin 2 is controlled in the range of
25.about.96.99 wt %, preferably 45.about.94.99 wt %, and the amount
of the phosphor 3c, 4c is controlled in the range of 3.about.65 wt
%, preferably 5.about.50 wt %.
[0064] Particularly, in order to obtain homogenous exhibition of
white light through the UV coating layer 1 for LED color
conversion, a mixture of the light diffusing beads having average
particle diameters of 1.about.4 .mu.m, 5.about.10 .mu.m and
11.about.30 .mu.m and mixed in a weight ratio of
1:0.4.about.0.8:0.1.about.0.3 may be used.
[0065] Optionally, the composition according to the present
invention may further include an organic or inorganic pigment in
order to control a color of the lighting device or the display
device. The organic or inorganic pigment may be present in an
amount of 0.1.about.3.0 wt %, preferably 0.1.about.1.0 wt %.
Advantageously, the organic pigment is used in view of
transparency. Examples of pigments include nitro pigments, azo
pigments, indanthrone pigments, thioindigo pigments, perylene
pigments, dioxazine pigments, quinacridone pigments, phthalocyanine
pigments, quinophthalone pigments, and the like, without being
limited thereto. For example, a yellow pigment for providing warmth
may be selected from among monoazo, diazo, naphthalazobenzene, cork
tree, goldthread, and mixtures thereof, without being limited
thereto.
[0066] Meanwhile, although there is no limitation to the thickness
of the UV coating for LED color conversion according to the present
invention, the UV coating generally has a thickness of 1.about.250
.mu.m, preferably 3.about.100 .mu.m.
[0067] Next, one embodiment of the invention wherein the UV coating
composition for LED color conversion is realized as a coating layer
1 will be described in more detail with reference to FIG. 3
illustrating an LED lens and FIGS. 5 and 6 illustrating light guide
plates 10, 10a, 10b.
[0068] FIG. 3 is a cross-sectional view of an LED lens 10 including
a UV coating layer 1 for LED color conversion according to the
present invention formed on a flat upper surface 7a thereof.
[0069] The LED lens according to the present invention has a
hemispherical shape with a wide upper section and a narrow lower
section, without being limited thereto. The LED lens is a typical
epoxy LED lens, which includes a flat upper surface 7a having an
annular lateral portion 7 and a flange 8 and is formed on a lower
surface thereof with a cylindrical LED mounting portion 9. The LED
mounting portion 9 is formed at an upper portion thereof with an
internally convex portion 7b. In addition, a UV coating composition
for LED color conversion is coated on the flat upper surface 7a to
form a coating layer 1, thereby allowing change of an emitted color
to be simply and easily carried out only by inserting a suitable
LED lens 10 of the present invention having the UV coating layer 1
for LED color conversion, irrespective of a predetermined color
emitted from a blue LED, a violet LED, a UV LED, or a white
LED.
[0070] In addition, the upper surface of the LED lens may have a
pectination shape, a plurality of dots, or a smooth planar shape in
order to provide soft illumination. Also, the upper surface of the
LED lens may have an opening at the center thereof as needed, a
forwardly projecting convex shape, a flat shape, a concave shape,
or other shapes. In this invention, the coating layer preferably
has a flat surface in order to ensure uniform distribution of
phosphors for color conversion.
[0071] Referring again to FIG. 4, a phosphor(s) 3c and/or 4c, light
diffusing beads 3b and/or 4b, and a pigment(s) 3a and/or 4a are
evenly dispersed in a UV-curable matrix resin 2.
[0072] As can be seen from FIG. 4, the UV coating composition 1 for
LED color conversion may be independently applied to the LED lens
or light guide plate without affecting the LED, such that a color
emitted from the LED can be easily and simply converted into white
light from blue, violet or UV light. Furthermore, scattering by the
light diffusing beads 3b and/or 4b allows the phosphor(s) 3c and/or
4c to sufficiently carry out conversion of the emitted color. Thus,
the phosphor can be very uniformly distributed without any problem
while significantly reducing or relieving glare or visual fatigue
caused by high brightness of the LED when a user directly views the
light source.
[0073] FIG. 5 is an exploded perspective view of one embodiment of
a backlight unit 100 including a light guide plate 10 having a
coating layer 1 (see an enlarge portion "B"), which is formed on a
light entering surface 12 thereof and is comprised of the UV
coating composition for LED color conversion according to the
present invention. Referring to FIG. 6, the backlight unit 10
includes a light source 15 including a plurality of LEDs 19, which
consist of one kind of LED selected from among blue, violet and UV
LEDs, a light guide plate 10 having the light entering surface
facing the light source 15, a reflective sheet 20 disposed below
the light guide plate 10, and a prism sheet 30, a light diffusing
sheet 40 and a protective sheet 50 sequentially stacked on an upper
surface of the light guide plate 10 constituting a light exiting
surface 11.
[0074] FIG. 6 is an exploded perspective view of one embodiment of
a backlight unit 100a including a light guide plate 10a having a
coating layer 1 (see an enlarge portion "C"), which is formed on a
light exiting surface 11 thereof and is comprised of the UV coating
composition for LED color conversion according to the present
invention. The backlight unit of FIG. 6 is substantially the same
as that shown in FIG. 5 except for the location of the coating
layer 1 comprised of the UV coating composition for LED color
conversion, and thus no further elaboration thereof is needed.
[0075] In the embodiments described above, as shown in an enlarged
portion "A" of FIG. 6, a pattern of prisms 14 each including prism
slopes 14a, 14b is formed on a lower surface 13 of the light guide
plate 10 or 10a.
[0076] FIG. 7 is an exploded perspective view of one embodiment of
a backlight unit 100b including a light guide plate 10b having a
coating layer 1 (see an enlarge portion "D"), which is formed on a
light entering surface 12 thereof and is comprised of the UV
coating composition for LED color conversion according to the
present invention. In this backlight unit, the light guide plate
10b has a pattern of internal prisms 18, which are formed on an
inner region thereof near the light entering surface 12 by laser
processing and comprise a plurality of longitudinal slits separated
from each other to be parallel to each other. In this embodiment,
the backlight unit 100b includes a light source 15 including a
plurality of LEDs 19, which consist of one kind of LED selected
from among blue, violet and UV LEDs, the light guide plate 10b
including the light entering surface 12, which has a UV coating
layer 1 for color conversion and faces the light source 15, a
reflective sheet 20 disposed below the light guide plate 10b, and a
protective sheet 50 disposed on an upper surface of the light guide
plate 10b constituting a light exiting surface 11. Except for these
components, the backlight unit 100b is substantially the same as
that of the other backlight units.
[0077] Therefore, in the backlight units 100, 100a, 100b each
including the UV coating composition for LED color conversion or
the coating layer 1 according to the present invention as shown in
FIGS. 5 to 7, there is no need for use of a white LED which is
relatively expensive and has a short lifespan, and relatively
inexpensive LEDs having a long lifespan, such as blue LEDs, violet
LEDs, or UV LEDs, may be used as the light source, such that a
predetermined color can be converted into white light through the
coating layer 1 comprised of the UV coating composition for LED
color conversion, thereby ensuring a long lifespan of the LED while
increasing economic feasibility.
[0078] In FIG. 6, the backlight unit is shown as including all of
the prism sheet 30, the light diffusing sheet 40, and the
protective sheet 50. However, when the UV coating layer 1 for LED
color conversion includes the light diffusing beads 3b, 4b, the UV
coating layer 1 may serve to perform the functions of the light
diffusing sheet 140 and the protective sheet 150, and the prism
sheet 130 is not an essential component for the backlight unit 100.
Therefore, all of these components can be omitted from the
backlight unit. As needed, with the prism sheet 30 attached to the
backlight unit, a UV coating layer 1 comprising the light diffusing
beads 3b, 4b is formed on the light exiting surface 11, whereby the
backlight unit 100a can be formed to have a thin and simple
structure, thereby providing good durability and economic
feasibility through reduction of manual labor and the number of
components.
[0079] Further, in FIG. 7, the light guide plate 10b has the
pattern of internal prisms 18, which are vertically formed on the
inner region thereof near the light entering surface 12 by focusing
laser beams emitted from a well-known laser oscillator to be
parallel to each other while being separated from each other in a
longitudinal direction, such that the pattern of internal prisms 18
thinly and uniformly distributes light emitted from the light
sources 19 in a transverse direction orthogonal to the light
sources 19 and a surface light source of uniform brightness can be
exhibited on the light exiting surface 11 by the pattern of prisms
14 formed on the lower surface 13 of the light guide plate 10b.
[0080] In this embodiment, since the pattern of internal prisms 18
is formed inside the light guide plate 10b, the light entering
surface 12 has a flat surface. Thus, the UV coating composition 1
containing the phosphor can be uniformly and easily coated on the
light guide plate 10b, with the phosphor uniformly dispersed
therein.
[0081] The light guide plates 10, 10a, 10b may be formed of any
well-known heat-resistant, transparent resin, such as acryl,
polycarbonate, and polymethyl (meth)acylate, crystal, glass, and
the like.
[0082] Further, in the backlight unit 100b of FIG. 7, the light
guide plate 10b includes the coating layer 1 formed by coating the
UV coating composition for LED color conversion on the flat light
entering surface 12 thereof, the pattern of internal prisms 18
formed on the inner region thereof near the light entering surface
12, and the pattern of prism 14 formed on the lower surface 13
thereof, so that only the protective sheet 50 can be stacked on the
light exiting surface 11, thereby providing a backlight unit 100b
having a thin and simple structure. However, it should be
understood that the present invention is not limited to this
configuration. Alternatively, instead of the protective sheet 50,
another coating layer 1a comprised of the UV coating composition
for LED color conversion containing light diffusing beads may be
further formed on the light exiting surface 111 in order to serve
as the light diffusing sheet and the protective sheet, whereby the
backlight unit can be significantly reduced in thickness and have a
simple structure, thereby providing good durability and economic
feasibility through reduction of manual labor and the number of
components.
[0083] Any kind of photoinitiator may be used for the composition
according to the present invention. Examples of the photoinitiator
may include alpha-hydroxyketone, phenylglyoxylate,
alpha-aminoketone, butyldihydroxyketone, an acylphosphine oxide,
and the like, which are widely used for UV-curable hard coating.
Preferably, alpha-hydroxyketone or phenylglyoxylate is used as the
photoinitiator in terms of light-transmitting properties. The
photoinitiator may be added in an amount of 0.1.about.8 wt %, and
more generally 0.1 to 4 wt %, based on the total weight of the
UV-curing resin. It should be understood that since selection and
the amount of these photoinitiators are well known in the art, the
amount of the photoinitiator is illustrated here as being included
in the weight of UV-curable resin without detailed consideration
thereof.
[0084] Further, the UV hard coating layer may be cured using a
mercury lamp or a xenon lamp with an exposure of 700.about.1300 mJ,
generally an exposure of 700.about.1000 mJ, at a wavelength of
350.about.400 nm for about 1.about.60 seconds, generally for about
10.about.30 seconds.
[0085] Hereinafter, the present invention will be described in more
detail with reference to examples.
Example 1
[0086] First, an LED lens was formed using an epoxy resin through
injection molding, as shown in FIG. 3. Then, a mixture of 92 wt %
of an epoxy acrylate monomer and an oligomer (containing 3.5 wt %
of alpha-hydroxyketone as a photoinitiator) and 8 wt % of
(YGd).sub.3Al.sub.5O.sub.12:Ce as a yellow phosphor was deposited
on an upper surface of the LED lens and subjected to irradiation
using a xenon lamp with an exposure of 890 mJ for 30 seconds,
thereby forming a 58 .mu.m thick UV coating layer for LED color
conversion.
[0087] The prepared LED lens was mounted on a blue LED. Upon
operation of the LED, slightly yellowish white light was
obtained.
Example 2
[0088] An LED lens was formed using an epoxy resin through
injection molding, and a mixture of 92 wt % of an epoxy acrylate
monomer and an oligomer (containing 3.5 wt % of alpha-hydroxyketone
as a photoinitiator), 6 wt % of (YGd).sub.3Al.sub.5O.sub.12:Ce as a
yellow phosphor, and 2 wt % of polymethyl (meth)acrylate having an
average particle diameter of 2.0 .mu.m (index of refraction: 1.50,
light transmittance: 91%) as light diffusing beads was deposited on
an upper surface of the LED lens and subjected to irradiation using
a xenon lamp with an exposure of 890 mJ for 30 seconds, thereby
forming a 85 .mu.m thick UV coating layer for LED color
conversion.
[0089] The prepared LED lens was mounted on a blue LED. Upon
operation of the LED, white light was obtained.
Example 3
[0090] A UV coating layer for LED color conversion was formed on a
flat upper surface of an epoxy LED lens by the same method as in
Example 1, except that a mixture of 87 wt % of an urethane acrylate
monomer and an oligomer (containing 1.8 wt % of phenylglyoxylate as
a photoinitiator), 7 wt % of Y.sub.2O.sub.2S:Eu,Gd as a red
phosphor, 3 wt % of ZnS:Cu,Al as a green phosphor, and 3 wt % of
polymethyl (meth)acrylate having an average particle diameter of
2.0 .mu.m as light diffusing beads was deposited on the flat upper
surface of the LED lens.
[0091] The prepared LED lens was mounted on a blue LED. Upon
operation of the LED, white light was obtained.
Example 4
[0092] A UV coating layer for LED color conversion was formed on a
flat upper surface of an epoxy LED lens by the same method as in
Example 1, except that a mixture of 92.5 wt % of an acryl acrylate
monomer and an oligomer (containing 1.5 wt % of phenylglyoxylate as
a photoinitiator), 3 wt % of LiAlO.sub.2:Mn as a red phosphor, 2 wt
% of Y.sub.3(Ga.sub.xAl.sub.1-x).sub.5O.sub.12:Ce (0<x<1) as
a green phosphor, 1 wt % of BaMgAl.sub.10O.sub.17 as a blue
phosphor, and 1.5 wt % of polymethyl (meth)acrylate having an
average particle diameter of 2.0 .mu.m as light diffusing beads was
deposited on the flat upper surface of the LED lens.
[0093] The prepared LED lens was mounted on a violet LED. Upon
operation of the LED, white light was obtained.
Example 5
[0094] On a light entering surface of a light guide plate as shown
in FIG. 5, a mixture of 95 wt % of a polyester acrylate monomer and
an oligomer (containing 2.5 wt % of alpha-hydroxyketone as a
photoinitiator) and 5 wt % of Sr.sub.2Ga.sub.2S.sub.5:Eu.sup.2+ as
a yellow phosphor was deposited and subjected to irradiation using
a xenon lamp with an exposure of 1000 mJ for 20 seconds, thereby
forming a 96 .mu.m thick UV coating layer for LED color
conversion.
[0095] When operating a backlight unit including the prepared light
guide plate and a blue LED, white light was obtained.
Example 6
[0096] On a light exiting surface of a light guide plate as shown
in FIG. 6, a mixture of 88 wt % of an epoxy acrylate monomer and an
oligomer (containing 3.5 wt % of alpha-hydroxyketone as a
photoinitiator), 5 wt % of Li.sub.2TiO.sub.3:Mn as a red phosphor,
4 wt % of Ca.sub.2MgSi.sub.2O.sub.7:Cl as a green phosphor, and 3
wt % of polycarbonate having an average particle diameter of 3.0
.mu.m (index of refraction: 1.59) as light diffusing beads was
deposited and subjected to irradiation using a xenon lamp with an
exposure of 1000 mJ for 28 seconds, thereby forming a 150 .mu.m
thick UV coating layer for LED color conversion.
[0097] When operating a backlight unit including the prepared light
guide plate and a blue LED, white light having high brightness was
obtained.
Example 7
[0098] On a light exiting surface of a light guide plate as shown
in FIG. 7, a mixture of 86 wt % of an epoxy acrylate monomer and an
oligomer (containing 2.2 wt % of phenylglyoxylate as a
photoinitiator), 5 wt % of LiAlO.sub.2:Mn as a red phosphor, 4 wt %
of Y.sub.3(Ga.sub.xAl.sub.1-x).sub.5O.sub.12:Ce (0<x<1) as a
green phosphor, 3 wt % of BaMgAl.sub.10O.sub.17 as a blue phosphor,
and 2 wt % of polymethyl (meth)acrylate having an average particle
diameter of 2.0 .mu.m as light diffusing beads was deposited and
subjected to irradiation using a xenon lamp with an exposure of
1000 mJ for 25 seconds, thereby forming a 100 .mu.m thick UV
coating layer for LED color conversion.
[0099] When operating a backlight unit including the prepared light
guide plate and a UV LED, white light having high brightness was
obtained.
Example 8
[0100] On a light exiting surface of a light guide plate as shown
in FIG. 7, a mixture of 79 wt % of a urethane acrylate monomer and
an oligomer (containing 3.5 wt % of alpha-hydroxyketone as a
photoinitiator), 8 wt % of LiAlO.sub.2:Mn as a red phosphor, 7 wt %
of Y.sub.3(Ga.sub.xAl.sub.1-x).sub.5O.sub.12:Ce (0<x<1) as a
green phosphor, and 6 wt % of BaMgAl.sub.10O.sub.17 as a blue
phosphor was deposited and subjected to irradiation using a xenon
lamp with an exposure of 1000 mJ for 25 seconds, thereby forming a
120 .mu.m thick UV coating layer for LED color conversion.
[0101] When operating a backlight unit including the prepared light
guide plate and a violet LED, white light having high brightness
was obtained.
Example 9
[0102] An LED lens was formed using an epoxy resin through
injection molding, and a mixture of 42 wt % of an epoxy acrylate
monomer and an oligomer (containing 5.5 wt % of alpha-hydroxyketone
as a photoinitiator), 46 wt % of (YGd).sub.3Al.sub.5O.sub.12:Ce as
a yellow phosphor, and 12 wt % of polymethyl (meth)acrylate having
an average particle diameter of 2.0 .mu.m (index of refraction:
1.50, light transmittance: 91%) as light diffusing beads was
deposited on an upper surface of the LED lens and subjected to
irradiation using a xenon lamp with an exposure of 890 mJ for 30
seconds, thereby forming a 63 .mu.m thick UV coating layer for LED
color conversion.
[0103] The prepared LED lens was mounted on a blue LED. Upon
operation of the LED, white light was obtained.
Example 10
[0104] A 38 .mu.m thick UV coating layer for LED color conversion
was formed on a flat lower surface of an epoxy LED lens having a
convex lens-shaped upper surface by the same method as in Example
9, except that a mixture of 45 wt % of an urethane acrylate monomer
and an oligomer (containing 6.8 wt % of phenylglyoxylate as a
photoinitiator), 27 wt % of Y.sub.2O.sub.2S:Eu,Gd as a red
phosphor, 23 wt % of ZnS:Cu,Al as a green phosphor, and 5 wt % of
polymethyl (meth)acrylate having an average particle diameter of
2.0 .mu.m as light diffusing beads was deposited on the flat lower
surface of the LED lens.
[0105] The prepared LED lens was mounted on a blue LED. Upon
operation of the LED, white light was obtained.
Example 11
[0106] A 56 .mu.m thick UV coating layer for LED color conversion
was formed on a flat upper surface of an epoxy LED lens by the same
method as in Example 9, except that a mixture of 40.0 wt % of an
acryl acrylate monomer and an oligomer (containing 7.5 wt % of
phenylglyoxylate as a photoinitiator), 20 wt % of LiAlO.sub.2:Mn as
a red phosphor, 15 wt % of
Y.sub.3(Ga.sub.xAl.sub.1-x).sub.5O.sub.12:Ce (0<x<1) as a
green phosphor, 15 wt % of BaMgAl.sub.10O.sub.17 as a blue
phosphor, and 10 wt % of polymethyl (meth)acrylate having an
average particle diameter of 2.0 .mu.m as light diffusing beads was
deposited on the flat upper surface of the LED lens.
[0107] The prepared LED lens was mounted on a violet LED. Upon
operation of the LED, white light was obtained.
Example 12
[0108] On a light entering surface of a light guide plate as shown
in FIG. 5, a mixture of 60 wt % of a polyester acrylate monomer and
an oligomer (containing 6.5 wt % of alpha-hydroxyketone as a
photoinitiator), 35 wt % of Sr.sub.2Ga.sub.2S.sub.5:Eu.sup.2+ as a
yellow phosphor, and 5 wt % of polymethyl (meth)acrylate having an
average particle diameter of 2.0 .mu.m as light diffusing beads was
deposited and subjected to irradiation using a xenon lamp with an
exposure of 1000 mJ for 20 seconds, thereby forming a 72 .mu.m
thick UV coating layer for LED color conversion.
[0109] When operating a backlight unit including the prepared light
guide plate and a blue LED, white light was obtained.
Example 13
[0110] On a light exiting surface of a light guide plate as shown
in FIG. 6, a mixture of 55 wt % of an epoxy acrylate monomer and an
oligomer (containing 3.5 wt % of alpha-hydroxyketone as a
photoinitiator), 25 wt % of Li.sub.2TiO.sub.3:Mn as a red phosphor,
15 wt % of Ca.sub.2MgSi.sub.2O.sub.2:Cl as a green phosphor, and 5
wt % of polycarbonate having an average particle diameter of 3.0
.mu.m (index of refraction: 1.59) as light diffusing beads was
deposited and subjected to irradiation using a xenon lamp with an
exposure of 1000 mJ for 28 seconds, thereby forming a 150 .mu.m
thick UV coating layer for LED color conversion.
[0111] When operating a backlight unit including the prepared light
guide plate and a blue LED, white light having high brightness was
obtained.
Example 14
[0112] On a light entering surface of a light guide plate as shown
in FIG. 7, a mixture of 50 wt % of an epoxy acrylate monomer and an
oligomer (containing 7.2 wt % of phenylglyoxylate as a
photoinitiator), 25 wt % of LiAlO.sub.2:Mn as a red phosphor, 12 wt
% of Y.sub.3(Ga.sub.xAl.sub.1-x).sub.5O.sub.12:Ce (0<x<1) as
a green phosphor, 10 wt % of BaMgAl.sub.10O.sub.17 as a blue
phosphor, and 3 wt % of polymethyl (meth)acrylate having an average
particle diameter of 2.0 .mu.m as light diffusing beads was
deposited and subjected to irradiation using a xenon lamp with an
exposure of 1000 mJ for 25 seconds, thereby forming a 48 .mu.m
thick UV coating layer for LED color conversion.
[0113] When operating a backlight unit including the prepared light
guide plate and a UV LED, white light having high brightness was
obtained.
INDUSTRIAL APPLICABILITY
[0114] The present invention provides a UV coating composition for
LED color conversion, which includes a phosphor for color
conversion and, optionally, a light diffusing bead and/or a
pigment, in a heat-resistant transparent UV-curable matrix resin to
allow white light for lighting or a display device to be obtained
through a simple and inexpensive structure from a high brightness
blue LED, violet LED or UV LED having a long lifespan without an
expensive white LED having a relatively short lifespan and high
brightness, which has a flat coating surface such that the phosphor
for color conversion can be uniformly distributed and coated
thereon, which can provide smoother and more comfortable
illumination by effectively relieving glare due to high brightness
of the LED when applied to lighting, and which permits compactness
and structural simplification when applied to a display device.
Therefore, the present invention has industrial applicability.
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